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The most detailed genetic map of the developing brain to date reveals networks that may influence our risk of developing five conditions, including schizophrenia and bipolar disorder. With further research, this could help scientists develop interventions that target these genetic pathways.

Various research groups have previously studied a relatively small number of brain samples to investigate how gene activity in the embryonic or fetal brain may influence a person’s later risk of certain conditions.

±·´Ç·É,Ìý at the University of California, Los Angeles, and her colleagues have analysed data from 654 donated embryonic or fetal brains – aged 4 to 39 weeks post-conception – from five previous studies.

The researchers compared the genes that were expressed in the brains with genetic variants that have previously been linked to five conditions: schizophrenia, bipolar disorder, attention deficit hyperactivity disorder (ADHD), autism and depression.

These links were based on relatively broad regions of the genome being associated with these conditions, which didn’t tell us much about the specific genes that interact to affect our risk, according to the researchers.

After analysing data from the embryonic and fetal brains, Wen and her colleagues pinpointed genetic pathways that provide more detail on 60 per cent of the genetic links previously identified for the five conditions.

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Some variants within these pathways can cause only certain parts of the DNA that codes for a gene to be used by a cell, rather than the gene’s entire code. This results in slightly different versions of proteins being created, which can alter brain cell activity and may raise the risk of these five conditions, according to the researchers.

These findings provide insights into the genetic architecture underlying these five conditions, which could potentially lead to new interventions for some of them, such as depression, says at Stanford University in California.

However, the researchers don’t know the circumstances of how the pregnancies ended before the embryos and fetuses were donated. If the pregnancies ended due to brain-related complications then the embryos and fetuses may not be representative of those that reach full-term, says Wen.